Part of his plan to get back to his best has been a decision to play with a larger 98-inch square frame racquet -- eight inches larger than his previous racquet.

Explaining his decision to try out the racquet in Hamburg earlier this week, Federer said on the ATP Tour website: "I've been very close on numerous occasions to changing racquets in a bigger way.

"But then very often, time was the issue. Maybe also just the records of grand slams - I was always keeping on playing quarters and semis - so then it was also a bit more difficult to change it because of the time.

"After I lost at Wimbledon, I thought this is a good time to go and test the racquets, to take a bit of time off and then add some tournaments and see was there enough time to change or not.

"I'm happy I did the change and now we'll see how it goes."

Federer -- who dropped from third to fifth in the world rankings after his Wimbledon loss -- will now head home to Switzerland to play at Gstaad next week.

Delbonis now faces Fabio Fognini for the Hamburg title after the Italian beat Spain's Nicolas Almagro 6-4 7-6 (7-1).